Your point is well taken. It is unlikely, though possible, that a relatively unknown itinerant preacher in 30 C.E. or so, would be called "rabbi" by anyone other that his closest and devout disciples, if even they would have used the term.
We don't have any evidence that I know of that Jesus received "semikhah" (as Hegg points out so well). If, as the Cath Ency. says, the term would be like "doctor" today, calling someone a "doctor" (as in one who is permitted to teach doctrine) who had not been licensed with the title by some legimate granting authority would be highly irregular, if not faintly fraudulent. Calling oneself doctor/rabbi would be worse.
I doubt that Jesus would have allowed himself to be called Rabbi, had he not been granted semikha, like Rabban Gamliel, Rabbi Yochanan ben Zakkai, etc. And if he had been granted semikha, one would think that he would have been called Rabbi throughout the New Testament.
I would still hold that calling Jesus rabbi is more than an unfortunate anachronism; it is an attempt to license him with a public title of authority that he probably did not have, and indeed, probably did not seek.
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